Neural mechanisms that underlie hemispheric lateralization for speech perception have not been definitively studied, despite the widely proclaimed importance of this phenomenon. Previous neurophysiological data indicate that species-specific communication sounds or 'calls' are asymmetrically represented in the Doppler-shifted Constant Frequency (DSCF) processing area of the primary auditory cortex of mustached bats. I propose to study inhibitory synaptic mechanisms that may create or shape an asymmetry in the responses to calls of cortical neurons on the right versus the left side. First, I will use frequency modulated (FM) sweeps of different slopes and bandwidths to determine the dynamic response areas on the right versus the left side. Second, for each side, I will compare responses of DSCF neurons to calls and FM stimuli before and after pharmacological removal of inhibition at the recording site. Third, in a few neurons, I will test the previously proposed hypothesis that hemispheric interactions contribute to hemispheric inequalities in call responsiveness. For these experiments, I will pair electrical stimulation of the right side with call stimuli and test if the application of BMI at the recording site on the left side reverses this effect.